Hi. In this video, we're going to extend the Hello World program, to make it a little bit more personal. So, we've left the application, as it was given to us earlier, with our Console.WriteLine, but it would be nice to make it more personal. So, what I'm going to do is add another Console.WriteLine, to our code, and inside there, prompt the user for their name. You'll notice that I've just repeated the line from beneath, Console.WriteLine. I've specified in quotes the piece of text I'd like to print to the console. You'll notice that goes in round brackets and you'll notice the semi-colon at the end of that line. All of these things are hugely significant. So, I'm going to create a variable of type string and call that variable Name. In C#, our variables have to what's called strongly typed, so every variable that we create has to be given or specify-, we have to specify a type for that variable, and the string basically means it can contain text. Any text that the user might enter. I'm going to make that equal to-, a call to Console.ReadLine.

You'll notice as I'm typing that Visual Studio pops up some little prompts. It's known as IntelliSense and it gives me options as the kind of thing that it thinks I'm trying to, to, to type. So, rather than carrying on typing ReadLine, I could cursor down and then hit the tab key to auto-select to complete that line. That's helpful because it means I've got no typos in there, and it makes a lot more sense to the editor. I will terminate that line with a semi-colon because, again, that's mandatory. So, the ReadLine statement is going to sit and wait for the user to type something in, and whatever they type in is going to get put into the thing on the left-hand side of the equals sign, this variable called Name. What I could then do is, rather than print 'Hello World' on this third line, I could get rid of the word 'World' and tack onto the end of this string the person's name. I can do that in a number of ways.

The classic way we used to do it is via something known as concatenation. So, I am tacking on the word name, with a plus sign, which means just join two strings together, and it should print the result out for me as I run that. And we'll try that out by running the application now by clicking the green triangle. And you can see that the application has prompted me to enter my name. I can type my name in, and I can press enter, and it prints out the words, 'Hello, Pete', which is very kind of it. So, we've managed to print out, 'Hello, Pete,' and with this concatenation going on. This is an old style way of formatting strings. There's a neater way of doing things these days. My favourite approach, out of a, a number of different approaches, is to prefix the thing in quotes with a dollar symbol, and that means we've got a formatted string. So, rather than having to tack things together with a plus symbol, we can embed the contents of variables into the string by using a curly bracket notation. And, inside the curly brackets we can put the name of our variable, in this case, Name, and which should have exactly the same effect as earlier, when we run this code.

So, I'm running the code now. The console pops up, asks for my name, I type my name in, press enter and exactly the same effect, 'Hello, Pete' gets printed to the console. It would be much more fun to get some additional input from our user, so I'm going to do another console at WriteLine. Notice, I'm using IntelliSense to help me write that fairly swiftly. I'm going to ask the user to also enter their age. And then, get that input from the user, and I'm going to put that input into a string by using another Console.ReadLine to get hold of that input. I can then concatenate that age onto the end of our output by, by extending the data in the string that we were trying to print, and typing in the words 'and your age is', and in the curly brackets, putting the word 'age'. If I ran that, we can see the app again prompts for my name.

It now prompts for my age. I'm not 21, but I'll pretend that I am, and we can see 'Hello, Pete, and your age is 21', which is also fine and interesting. One other thing I'd like to look at here is to be able to do arithmetic with our data. And so, what I'd like to be able to do is add one to the age, because maybe it's my birthday. And, classically, we would do that by saying something like 'Age equals age plus one'. So, take the value in 'age', add one to it, and put it back into the variable that it came from. But, we're not going to get the effect that we, kind of, expect by running the code as it stands. So, if I run it, it looks like it's okay. We get the same prompt coming up, I type in my name, I type in my age, 21, but you'll notice what it prints out, 'Your age is 211,' which is a fairly dramatic increase in age when all you're trying to do is add one to it. The reasoning behind that is it's treating age as a string, and it's doing concatenation rather than arithmetic.

So, the solution would be not to declare age as a string, but to declare it as what's known as an integer, but, unfortunately, Console.ReadLine returns strings. It's the only thing you can get from the user. So, the work around to solve that problem is to call Convert.ToInt32. So, there's a convert class that has a, a load of ready built functionality in it, one of which is the ToInt32, that takes strings and tries to convert them to integers. That means as long as I type in something that can be converted to an integer, this line of code will be just fine. I'll be able to add one to my age and be 22 rather than 211. So, I run the application, get the prompt up to type in my name. I type in my age, 21, and it says, 'Hello, Pete. Your age is 22.' So, we've managed to get hold of that data, convert it to an integer type and print it out.

So, in this little video we've extended the Hello World program, and we've seen how we can prompt the user for input, and we can get hold of different types of input strings and integers, convert the input of string to an integer and do arithmetic with that integer.

Practical example of some C# basics

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